1. Field of the Invention
This invention generally relates to floorplanning. More specifically, the invention relates to a method and system to decide the positions of circuit blocks or IP blocks on an integrated circuit in order to obtain an optimal wire length.
2. Background Art
Floorplanning is to decide the positions of circuit blocks or IP blocks on a chip subject to various objectives. It is the early stage of physical design and determines the overall chip performance. Due to the enormous complexity of VLSI design with continuous scaling-down of technology, a hierarchical approach is needed for the circuit design in order to reduce runtime and improve solution quality. Also, IP (module reuse) based design methodology becomes widely adopted. This trend makes floorplanning even more important.
Floorplanning can be classified into two categories, slicing and non-slicing. Among slicing representations, there are binary tree and normalized Polish expression. For non-slicing structure, many representations are invented recently, such as topology representation (BSG, sequence pair, TCG), packing representation (O-tree, B*-tree), and mosaic representation (CBL, Q-sequence, twin binary tree, twin binary sequence). All of these algorithms compact blocks to the left and bottom subject to the given topological constraints. Recently, additional constraints are addressed in floorplanning, such as fixed frame, alignment and performance (bounded net delay), buffer planning in floorplanning, etc. Again, within the approaches, the floorplan is compacted to lower-left (or upper-right) corner and then evaluated. In general, compaction implies minimum area. However, it may be sub-optimal for other objectives, such as minimizing wire length, routing congestion, and buffer allocation. As we can see, even with the same minimum area and the same topology, there exists lots of different floorplans that have different distribution of white space and thus have different values on other objectives.
In floorplanning and placement, minimizing total wire length is the first-order objective. If a floorplanner/placer can minimize total wire length very well, then there is much freedom and space to consider and tradeoff other concerns such as routability and timing. It is not known in the prior art how to place blocks to obtain an optimal wire length.